Fluid actuated cylinders are used extensively in industrial manufacturing processes including both light and heavy machinery. For instance, fluid actuated cylinders are employed to open and closed industrial tank covers, in reciprocating squeegee assemblies, for immersing cleaning baskets containing machine parts in cleaning tanks, and any other application where the reciprocating motion of the cylinder assembly can be harnessed to perform a particular task.
Referring to FIG. 1, there is shown a typical prior art fluid actuated cylinder 10 comprising a cylinder body 12 having a closed end 14 and an open end 16. The cylinder body 12 presents a bore 18 for receiving a piston rod assembly 20 comprising a piston 22 and piston rod 24. The piston rod assembly 20 reciprocates within the bore 18 along the longitudinal axis 26 of the cylinder body 12. The free end 28 of the piston rod extends through the open end 16 of the cylinder body 12 and is adapted to be connected to an object to be operated either directly or by some sort of linkage arrangement.
A pair of spaced apart ports 30 and 32 are provided on the cylinder body 12 for receiving and exhausting either air or a hydraulic oil depending upon whether the cylinder assembly is designed to be actuated pneumatically or hydraulically. The first port 30 is located adjacent to the closed end 14 of the cylinder body 12 and operates to supply air or oil to the cylinder 10. The second port 32 is located adjacent the open end 16 of the cylinder body 12 and operates to exhaust the air or oil from the cylinder 10.
Problems can arise when the above-described cylinder is employed in an application where the reciprocating piston rod assembly is connected to the object to be operated by a linkage arrangement. In such applications, the geometry of the linkage transfers bending torques to the piston rod of the cylinder. These bending torques can be quite substantial if the object being operated is heavy and can cause binding and bending of the piston rod. This in turn can cause premature wear of the piston and or cylinder bore. The bending torques can also cause premature wear of the bearings in the connecting linkage.
An application where these bending torques can be extreme is where the cylinder is implemented for the purpose of lifting baskets or containers of parts in and out of immersion cleaning devices. Immersion cleaning devices are employed in many different industries to clean various items such as newly machined metal parts. An example of such an immersion cleaning device is shown in U.S. Pat. No. 5,299,587 entitled ROTATING AND RECIPROCATING IMMERSION CLEANING APPARATUS AND METHOD issued to Frederick Randall et al. and assigned to Randall Manufacturing Company, the assignee herein. To increase productivity, it is desirable to clean these parts in bulk. Typically, the parts are loaded into baskets or other like containers and then immersed into a cleaning tank. Since the baskets are heavy and awkward, it is desirable to lower and raise the baskets mechanically. The employment of fluid actuated cylinders for such purposes is well known.
In FIGS. 2A and 2B, the prior art fluid actuated cylinder 10 of FIG. 1 is shown in conjunction with an immersion cleaning device. The immersion cleaning device comprises a tank 40 and includes a rear side wall 42. The cylinder 10 is secured to the rear side wall 42 of the tank 40 by a mounting assembly comprising a pair of vertically extending U-shaped guide channels 58 and 60. The open portion of the channels are oriented in opposing relationship with each other. A horizontally extending bottom mounting plate 54 couples the pair of guide channels 58 and 60 together at their lower most ends and supports the closed end 14 of cylinder body 12. A horizontally extending upper mounting plate 56 extends between the pair of guide channels in a location adjacent to the open end 16 of cylinder body 12. An upper spacer bracket 46 and lower spacer bracket 44 provides a structure on the wall of the tank for fastening the mounting assembly to the tank.
The closed end 14 of cylinder body 12 includes a cylinder mounting dowel 52 which is received by an aperture formed in the bottom mounting plate 54. This arrangement assures that the lower most portion of the cylinder 10 is securely abutting against the lower spacer bracket 44 thereby providing a fixed mounting of the lower most end of the cylinder body 12.
The marginal upper most portion of the cylinder body 12 is rigidly mounted via the upper mounting plate 56 such that it abuts against the upper spacer bracket 46. This prevents side to side and front to rear movement of the cylinder.
The free end 28 of the piston rod 24 is coupled to a horizontally extending linkage member 48 which extends over the interior of the tank 40. An elevator shaft 50 depends vertically from the linkage member 48. The end of the elevator shaft 50 is adapted to hold a basket (not shown) which contains the parts to be immersed within the cleaning fluid of the tank 40. A sliding block 62 is coupled to the linkage member 48 just above the free end 28 of piston rod 24. Each end of the sliding block 62 rides up and down in a corresponding guide channel to vertically guide the linkage 48 and elevator shaft 50 so that the basket is lowered in and raised out of the tank 40 as the piston rod assembly 20 reciprocates within the cylinder body 12.
The rigid mounting of both the marginal upper end of the cylinder and the lower most end of the cylinder prevents the cylinder from moving or aligning itself in response to the bending torques that are exerted against it as the piston rod assembly 20 reciprocates within the cylinder body 12.
The prior art has attempted to solve the above-described problem by providing various techniques for allowing the cylinder to move or float in response to various bending forces acting upon the cylinder. For example, U.S. Pat. No. 4,944,215 issued to Nimmi on Jul. 31, 1990, entitled FLUID ACTIVATED CYLINDER ASSEMBLY WITH A FLOATING CYLINDER HEAD discloses a cylinder wherein the piston shaft is free to move through a predetermined range within the cylinder. This is accomplished by using a fairly complex piston rod seal and spherical piston arrangement.
It is therefore, an object of the present invention to provide an improved fluid actuated cylinder which comprises a standard piston rod assembly and means for allowing the cylinder to float with respect to its mounting fixture thereby preventing wear and fluid leakage of the cylinder as a result of misalignment of the piston rod with respect to the longitudinal axis of the cylinder.